1. Field of the Invention
The present invention concerns a device for an electrophotographic apparatus, and more particularly, a device for detecting the toner in the developing unit of an electrophotographic apparatus.
2. Description of the Related Art
Monitoring the level of toner in a developing unit is crucial for the proper operation of an electrophotographic apparatus during a printing process. An electrophotographic apparatus can be either one of a laser printer, an electronic copier, a facsimile machine, or any versatile office machine. The general operation of an electrophotographic apparatus starts with paper being loaded as from a supply tray and then transported through to a high pressure transfer unit. The high pressure transfer unit places the toner image onto the sheet of paper. Subsequently, the paper is transported to a fixing device that fixes the toner image onto the paper using both heat and pressure rollers.
To prepare the toner image for the high pressure transfer unit, it is necessary to attach toner particles to the latent electrostatic image on the photoconductive drum. The toner particles are applied by the developing unit, thereby transforming the latent electrostatic image into a latent toner image. Thus, the level of toner in the developing unit is critical to the proper operation of the electrophotographic apparatus. This importance has lead to many developments in toner detection methods. By way of example, U.S. Pat. No. 5,621,221 to Shinohara entitled Toner End Detection Device And Method, mentions a toner cartridge that has a light source and light sensor fixed near a bottom comer of the cartridge in order to detect when the toner is exhausted. U.S. Pat. No. 5,036,358 to Yoshida entitled Image Forming Apparatus And A Method For A Detecting Developer Amount Therein shows a toner cartridge with a light emitting device on the top of a toner cartridge and a second light receiving device on the bottom of the toner cartridge. U.S. Pat. No. 5,589,918 to Oshida entitled Process Cartridge, Assembling Method Therefore And Electrophotographic Apparatus and U.S. Pat. No. 5,521,684 to Takahashi entitled Image Forming Apparatus Including Optical Element For Optically Detecting Amount of Developing Agent In Developer, both disclose using light emitting and light receiving elements oriented linearly in a manner perpendicular relative to the base of the printer.
I have observed that what is needed, but so far unaddressed by the prior art, is a toner detection device that utilizes a light emitting element located on the side of a toner cartridge and a receiving element located in a recess in the bottom of the cartridge, that uses only one recess to accommodate the light transmission elements, than can be used with a diode light from the scanner being substituted for the separate light emitting element, and that measures the transmitted light by either the frequency or intensity of the light received by the photoreceptor. I expect that such a device would be more economical to manufacture thereby improving productivity and efficiency in the manufacturing process.